I know plenty of risk management experts. I’m not one. But I know enough to know that mask-wearing when indoors with other people is a no-brainer. Not to mention just the decent thing to do.

I’ve spent a fair amount of time wrestling with risk assessments, mostly to do with corruption and data protection: planning them, doing them, revising them, advising on them, responding to them. I know plenty of people who’re far more expert in assessing and managing risk than I am. But I’ve learned enough to prize some of the fundamentals. And to realise how they can be applied more generally.

Say – just for instance – to how us normal human beings should respond to Covid, the easing lockdown, and any attempt to get back to a new normal. Particularly where facemasks are concerned.

The experts will wince at the next bit, when I try to boil down the bare basics of risk management into easy-to-digest chunks for the hard of thinking (like me, in this regard). Apologies in advance for how simplistic this is.

But fundamentally you assess risk and respond to it in three stages.

First, you work out what your risks are. Forget about whether they’re everyday or one-in-a-million for a minute. What could go wrong – not for any organisation, but specifically for yours? In a large organisation this can be a mammoth task, involving questionnaires, interviews, meetings and lord knows what else. But for small groups it’s essentially a test of imagination, and being honest with yourself.

Secondly, For each risk, try to assess how much you should worry about it, which is primarily about answering two questions:

• How likely is it that it could happen?
• And how bad would it be if it did?

Everyone will have their own way of combining these two factors – often there’s a three- or five-step measure for both probability (the first question) and impact (the second), and some kind of matrix to tell you what combinations you should really worry about. But often a RAG (red/amber/green for high/medium/low) rating is good enough, where you focus particularly on anything amber/red or with two reds (although depending on the circumstances green/reds and amber/ambers may at least need a bit of thought).

Third and finally comes the really important bit: what do you do about it. The classic four choices (not all of them exclusive, of course) are:

• Avoid: just don’t run the risk at all. A company, for instance, could decide simply not to do business in certain jurisdictions.
• Transfer: insure against it, so someone else picks up the tab. For anyone who drives a car, this will sound familiar.
• Mitigate: what steps can you take to reduce the risk? How well will any given mitigant work? The best mitigants, of course, help with more than one risk.
• Accept: sometimes you just have to suck it up. Particularly for relatively low-impact risks, this may be the only cost-effective answer.

So what does this have to do with mask-wearing? (And yes, I know we were told for months that it wasn’t worth it, that the evidence for it being helpful was marginal at best, that it didn’t really protect you from other people. Although how much of that was solid and how much was really about mitigating – there we go – the disastrous and negligent PPE shortage is anyone’s guess.)

Well, let’s walk through the steps.

1. The risk is obvious. It’s getting Covid when in an enclosed space with people other than my household. Or giving it to someone in the same environment. (OK. Two risks. Easy to overlook the second one, though.)
2. Impact: really high. Yes, I or the person I give it to might get lucky. (And yes, I already did – given that my dose of The Bug was horrible for a couple of weeks and now seems to have wholly departed. I’m humbled by how fortunate I was.) But those odds suck. Probability: also pretty high. And – what’s worse – impossible to calculate with any reliability, given that neither I nor anyone else will know we’re infectious until it’s far too late to avoid hurting people. I’m calling this Amber-Red at least, and probably Red-Red.
3. Response: can I avoid it? Short of becoming an anchorite, no. Can I transfer it? No. Insurance won’t stop me from dying. Can I just accept it? Well, maybe if it was just about me – but it’s not. This is about the large and fundamentally uncalculable risk I pose to others. Call me judgmental, but prioritising my freedom if it puts others at grave risk just seems unutterably selfish and inhuman.

So what’s left? Mitigation. What can I do? I can wash my hands. Effective and easy. I can keep my distance. Less easy – yes, I’m looking at you, the gin-in-a-can buyers in Aldi yesterday who insisted on standing 18 inches from my back in the queue yesterday while laughing raucously. And problematic in some jobs and workplaces. But no reason not to do it to the extent reasonably possible.

And masks. Yes, masks. I can’t help noticing that most of the countries who are beating this thing take mask-wearing as a given. Japan, in particular, which was late as we were in taking concrete steps to protect its citizens, seems to have done surprisingly well. A place where mask-wearing to protect others when you’re sick is regarded as about as basic a propriety as not being naked on public transport. (I realise there are a number of other potential reasons for Japan having escaped our fate. But the consistency across habitual mask-wearing states is interesting.)

Even if – as some suggest – the benefit from masks is marginal, marginal makes a pretty big impact when multiplied across a multi-million-strong population. And where R is close to 1, or ticking above it, marginal becomes even more important. Literally (and imagine how much it pains a pedant like me to use that word) a life-and-death difference.

I recognise there will be medical reasons not to. I recognise it’s hard or impossible for small kids. I recognise (from personal experience) how damned annoying it is with fogged-up glasses.

But what it comes down to is this: I am my sister’s keeper, my brother’s keeper. I don’t know if I’m dangerous to them. I can reduce the chances of me hurting them by putting a mask on when indoors with others, at minimal cost to myself. So I’m going to. Please do likewise.

(Note: from everything I’ve seen, this is fundamentally an inside problem, not an outdoors one. I tend not to mask up when I walk down the street, or run, or cycle (although I do everything I can to keep my distance), and I wouldn’t blame anyone else for doing likewise. But in a shop, or an office, or a place of worship, or anywhere else which is indoors… well, just put the thing on, OK?)